After applying a position tolerance to a hole pattern, how is its orientation related to datums?

After applying a position tolerance to a hole pattern, how is its orientation related to datums?

• A. It may rotate freely as long as centers are within tolerance
• B. It must align exactly with a single datum axis
• C. It must be located and oriented within the DRF relative to the datums
• D. Orientation is not considered in GD&T

Answer: (C)

The point of this item is that a position tolerance on a hole pattern is evaluated with respect to a datum reference frame, which fixes both how the part is oriented in space and where features must lie. When a position tolerance is applied, the centers of the holes must fall within the cylindrical tolerance zone defined in the DRF and, crucially, the entire pattern must be oriented relative to the datums as defined by that DRF. If the pattern were allowed to rotate independently of the datums, the centers would move in relation to the DRF and would likely exceed the tolerance, even if their centers stayed within the cylinder in some other orientation. Therefore, the pattern must be located and oriented within the DRF relative to the datums. This is why that choice is the best: it captures that both position and orientation are constrained by the datum reference frame.

The point of this item is that a position tolerance on a hole pattern is evaluated with respect to a datum reference frame, which fixes both how the part is oriented in space and where features must lie. When a position tolerance is applied, the centers of the holes must fall within the cylindrical tolerance zone defined in the DRF and, crucially, the entire pattern must be oriented relative to the datums as defined by that DRF. If the pattern were allowed to rotate independently of the datums, the centers would move in relation to the DRF and would likely exceed the tolerance, even if their centers stayed within the cylinder in some other orientation. Therefore, the pattern must be located and oriented within the DRF relative to the datums. This is why that choice is the best: it captures that both position and orientation are constrained by the datum reference frame.